Electron Transport Studies
Electron transport in fusion plasmas is intensively studied. Great progress in physics understanding has been achieved during the last years and the main recent results are reviewed here. In particular, it appears that a threshold in normalised gradient explains most of the observations, both in steady-state and transient conditions. Comparisons between turbulence theory and experimental results convincingly suggest that the trapped electron modes dominate electron transport at low and moderate collisionality, when electron heating dominates. The threshold for these modes agrees with the experimental values. The stabilisation of these modes at high collisionality, as predicted by theory, is found in the experiments. Electron transport is then driven by the ion temperature gradient modes. At low collisionality, if trapped electron modes are stabilised by negative shear and shafranov shift effects, electron internal transport barriers may develop. This topic is also briefly addressed.